Motorized gates and doors are well known access restricting or security devices for parking lots, buildings and other restricted areas. All such devices will hereinafter be referenced to as "motorized gates". Typically, motorized gates include a motor for opening and closing the gate and an electronic gate controller for controlling operation of the gate motor. The electronic controller may be responsive to a sensor, key, switch, token or other access granting device for opening and closing the gate. A power supply, typically an alternating current (AC) power supply, provides electrical power to the electronic gate controller.
A persistent problem for known motorized gates is the need to allow these gates to open upon loss of electrical power thereto. Such loss of electrical power may occur as a result of a lightning storm, fire, or other disaster, or as a result of commonly occurring power outages. In the event of a loss of power, the inability to open the gate may produce an inconvenience for those in the area who must wait until power is restored in order to leave or enter the area. More importantly, in an emergency or disaster situation, loss of power may trap people in the area preventing evacuation and preventing the entrance of emergency personnel. Accordingly, local ordinances often require motorized gates to provide for opening upon loss of electrical power. Many insurance companies also require the inclusion of a manual override to allow opening the motorized gate upon loss of electrical power.
A simple solution for allowing a motorized gate to be opened upon loss of power is a manual release. The manual release may unlock the gate from the gate motor, so that the gate may be manually opened. However, such a manual release must be mounted inside the restricted area to prevent unauthorized persons from activating the manual release and thereby gaining access to the restricted area. Unfortunately, by placing the manual means inside the gate, activation by fire or other emergency personnel outside the restricted area is precluded.
Another manual gate override is disclosed in U.S. Pat. No. 4,658,543 to Carr, which illustrates a controller which is connected between the main power supply and the gate motor. If there is a malfunction or a power outage, a manual bypass switch allows the user to bypass the controller and directly connect a standby battery to the motor to thereby operate the gate. Unfortunately, as stated above, such a manual bypass switch allows a bypass by unauthorized personnel. Moreover, a battery powered bypass which allows opening and closing the gate under backup battery power may allow the battery to discharge when the gate is in the closed position, thereby again preventing opening of the gate. A manual bypass also precludes automatic operation during an emergency situation.
It is also known in the art to employ a backup door opening system which opens a non-motorized door in response to a power outage. For example, U.S. Pat. No. 4,129,811 to Pearson discloses an emergency door opening system which operates in connection with a ventilation system used in barns or other structures which house animals. The ventilating system normally provides air ventilation to the barn. When power to the ventilating system is lost, a relay system energizes a battery powered motor to open a door on the barn and provide emergency ventilation. The Pearson reference does not disclose or suggest a backup system which could be employed with a motorized gate, the motor of which opens and closes during normal use, to allow operation of the motorized gate upon loss of electrical power.
The art has heretofore suggested other systems for operating a motorized gate in the event of power loss thereto. For example, U.S. Pat. No. 4,490,624 to Luker discloses a door control apparatus for an automatic door which includes a main power supply which normally drives a main door motor to open and close the door. A second battery power supply is provided to operate a second door motor. A relay detects when there is a main power supply failure and thereby connects the battery to the second motor for driving the door via a common drive assembly. Unfortunately, the Luker reference requires the use of a second drive motor for emergency conditions. The need for a second motor adds greatly to the cost, and makes it difficult to adapt the system to existing motorized doors or gates.
The art has also heretofore provided uninterruptable power supplies (UPS) for use in connection with computers or other critical systems. A UPS, for example as described in U.S. Pat. No. 4,675,538 to Epstein, typically substitutes a backup battery for the normal AC power service upon loss of normal AC power. However, such UPS's are not appropriate for use in motorized gates for at least two reasons. First, a UPS will continue to allow the motorized gate to open and close until its battery discharges. If the battery discharges when the gate is closed, emergency exit and entry is again prevented. Moreover, UPS's tend to be expensive because they are designed to provide uninterrupted power with a smooth switch over in addition to long term battery power for use during long power losses. While this expense may be justified for computer systems, the expense would preclude use of a UPS with a motorized gate.
Backup power supplies have also been incorporated into other expensive equipment. For example, U.S. Pat. No. 4,791,443 to Foley et al. discloses a backup power supply for photographic processing equipment which allows any film in progress to be processed. There is no disclosure or suggestion of any backup power supply for a motorized gate.